French fryers in common use employ tubular, metal-sheathed electric heating elements, such as of the type shown in U.S. Pat. No. 3,908,531, issued to Fred W. Morley on Sept. 30, 1975. Contact of the oil with the round cross-sectioned sheath is limited and therefore more time was required to bring the oil up to frying temperature.
In an attempt to increase the surface contact with the oil, strip heaters were used, but where the insulation within the heater was mica, wattage was limited because mica cannot withstand the high heat required in deep fat frying.
Strip heaters are also available wherein the insulation is compacted, granular material, such as disclosed in U.S. Pat. No. 1,614,330, issued Jan. 11, 1927, to Edwin L. Wiegand. Although the wattage problem was reduced with this type of heater, the assembly of a plurality of these strip heaters to provide side-by-side heating portions and upright terminal portions represented a substantial and costly assembly.
Our invention eliminates the problems of the prior art, as noted above, and provides a heater capable of high wattage, low manufacturing cost and with substantial surface contact with the liquid to be heated. The low cost is achieved by use of standard tubular, metal-sheathed heaters which are produced in large quantities for a multitude of uses, such as for surface, broiler and bake elements in an electric range; immersion heaters of various types; circulation heaters; and many other uses.
According to our invention, two or more standard tubular, metal-sheathed heaters are slid into an empty metal tube having a selected interior diameter, wall thickness and length. The assembly is then flat-pressed in the appropriate longitudinal places therealong, and the pressed heater is then bent to produce a shape required by a user.